1. Field of the Invention
This invention relates to an improved efficiency polarized light source. More particularly, it describes an apparatus for and method of recovering optical energy normally discarded in converting a source of non-polarized light to polarized light.
2. Summary of the Prior Art
Linearly polarized light, also called plane polarized light, is light for which the spatial orientation of its electric field lies entirely within one plane. There are numerous devices which use linearly polarized light. Many light valves and optical processors need linearly polarized light. Often in order to polarize a light beam, the beam is passed through a polaroid sheet or polarizing beam splitter. Theoretically, the polarizing process consists of separating any two orthogonal components of the electric field.
In the prior art, two methods of producing polarized light, reflection and absorption, are used. Both methods are inefficient. If a polarizing sheet is used, then the energy of one of the polarization states is simply absorbed. If a polarizing beam splitter is used then the light consisting of the second polarization state is deflected away from the primary optical path and allowed to dissipate. In both methods roughly half of the energy of the initial light source is lost. For many applications this is not important. However, there are certain applications where the efficiency with which non-polarized light is converted to polarized light is important.
Relevant prior art includes U.S. Pat. No. 4,516,837 issued to Soref et al., and U.S. Pat. No. 4,461,543, issued to McMahon. Both patents use related combinations of components, but for different purposes. Both Soref and McMahon describe optical switches for optical transmissive systems and both use polarizing beam splitters to create two or more polarized light beams which can then be modulated. The modulated beam may then be recombined to create a single switchable non-polarized light beam. The apparatus does not provide a source of polarized light with improved efficiency.